Method and device for distance detection

ABSTRACT

A distance detection apparatus cancels signal delay times of transmission and reception circuits ( 13, 15, 22, 25 ), which are causes of the errors of distance detection, by receiving a transmission signal turned back directly to measure the difference between the transmission timing and the reception timing at that time, and by setting the value obtained by the measurement as a correction value at the time of obtaining the measurement distance.

TECHNICAL FIELD

The present invention relates to a distance detection apparatus and amethod therefor, both suitable for detecting a relative distance betweenmobile stations or a relative distance between a mobile station and abase station. In particular, the present invention relates to a distancedetection apparatus and a method therefor, both suitably applicable to amobile communication system in conformity with the spectrum spreadingcommunication mode.

BACKGROUND ART

Conventionally, there has been developed a distance detection apparatusfor detecting a relative distance between two mobiles by means of thecommunication conforming to the spectrum spreading communication mode.For example, in the vehicle communication apparatus disclosed inJapanese Laid-Open Publication No. HEI 5-122120, when a certaincommunication station MS-1 transmitted a radio wave modulated inconformity with the spreading modulation to another communicationstation MS-2 and the communication station MS-2 received the transmittedwave, the communication station MS-2 transmits a radio wave modulated inconformity with the spreading modulation by the use of a spreading codesynchronized with the spreading code of the received wave back to thecommunication station MS-1.

When the communication station MS-1 received the responded wave from thecommunication station MS-2, the communication station MS-1 detects theperiod of time from the transmission of the radio wave to the receptionof the responded wave from the communication station MS-2, and detectsthe relative distance between the communication station MS-1 and thecommunication station MS-2 on the basis of the following formula (1).

Relative Distance=(Light velocity)×(Time Difference)/2  (1)

However, the aforesaid vehicle communication apparatus has a problemthat it cannot perform the distance detection with high accuracy owingto signal delays in the transmission circuits thereof and the receptioncircuits thereof.

DISCLOSURE OF INVENTION

The present invention was invented in consideration of the problem, andaims to provide a method for detecting distance and a distance detectionapparatus, both capable of removing the errors of distance detectioncaused by signal delays in the transmission circuits thereof and thereception circuits thereof.

A method for detecting a distance according to the present invention isa method for detecting a distance by measuring the propagation time ofan electromagnetic wave, and the method inputs a transmission signaloutput from a transmission system circuit directly into a receptionsystem circuit, and obtains the signal delay time of the transmissionand reception circuit by measuring a difference between the receptiontiming of the transmission signal that has passed through the receptionsystem circuit and the transmission timing of the transmission signal,and then performs the correction of the measured distance by using theobtained signal delay time.

According to the method, the sum of the signal delay time of thetransmission system circuit and the signal delay time of the receptionsystem circuit are measured, and the measured sum of the signal delaytimes is used as a correction value at the time of obtaining ameasurement distance. Consequently, respective signal delay times of thetransmission system circuit and the reception system circuit arecanceled. Thereby, distance detection with high accuracy becomespossible.

Moreover, a method for detecting a distance according to the presentinvention receives a reflection signal of a transmission signal from anobject of distance measurement, and measures the phase differencebetween the reception signal and the transmission signal, and detectsthe relative distance to the object of distance measurement on the basisof the measurement result, and further corrects the detected relativedistance by means of the signal delay time in a transmission andreception circuit, the signal delay time being a measurement result ofthe difference between the reception timing of the transmission signalin the reception system circuit and the transmission timing of thetransmission signal.

According to the method, the sum of the signal delay time of thetransmission system circuit and the signal delay time of the receptionsystem circuit is measured, and the measured sum of the signal delaytimes is used as a correction value at the time of obtaining ameasurement distance to the object of distance measurement.Consequently, respective signal delay times of the transmission systemcircuit and the reception system circuit are canceled. Thereby, distancedetection with high accuracy becomes possible.

Moreover, a distance detection apparatus according to the presentinvention adopts a configuration comprising: a transmission systemcircuit in which a timer of a self station generates a periodic signalthat is transmitted to an opponent station; a reception system circuitfor receiving a periodic signal generated by a timer of the opponentstation and transmitted to the self station; a signal path for inputtingthe transmission signal from the transmission system circuit to thereception system circuit directly; and a distance detection section formeasuring a difference between the transmission timing at the time ofthe transmission of the signal from the transmission system circuit andthe reception timing at the time of the input of transmission signal tothe reception system circuit through the signal path to obtain a selfstation signal delay time, and for measuring a quantity of discrepancybetween a reception timing of the transmission signal from the opponentstation and the reference timing of the timer of the self station toobtain a self station detection phase difference, and for detecting arelative distance between the self station and the opponent station bythe use of the self station signal delay time, the self stationdetection phase difference, the opponent station signal delay timeobtained by the opponent station, and the opponent station detectionphase difference.

According to the configuration, by the measurement of the respectivesums of the signal delay times of the transmission system circuits andthe signal delay times of the reception system circuits of the twocommunication stations, and by the use of the respective sums of thesignal delay times as correction values at the time of the obtainment ofa relative distance between the two communication stations, signal delaytimes of the respective transmission system circuits and the respectivereception system circuits of the two communication stations arecanceled, and then distance detection with high accuracy becomespossible.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the basic configuration of thedistance detection apparatus according to embodiment 1 of the presentinvention;

FIG. 2 is a block diagram showing the configuration of the distancedetection apparatus according to embodiment 7 of the present invention;and

FIG. 3 is a timing chart for illustrating a delay profile of thedistance detection apparatus according to embodiment 8.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described byreference to the attached drawings.

(Embodiment 1)

FIG. 1 is a block diagram showing the basic configuration of thedistance detection apparatus according to the embodiment 1 of thepresent invention. In the figure, the distance detection apparatusaccording to the embodiment 1 are severally mounted on communicationstations 10, 20 for transmitting signals and receiving them by means ofelectric waves. The communication stations 10, 26 includes referencetimers 11, 21, signal generation sections 12, 24, transmission systemcircuits 13, 25, signal reception sections 14, 23, reception systemcircuits 15, 22 and antennas 16, 26 for both of transmitting andreceiving.

In the distance detection apparatus according to the embodiment 1, thesignal generation section 12 and the signal reception section 14 in thecommunication station 10 on one side and the signal reception section 23and the signal generation section 24 in the communication station 20 onthe other side are embodied as microcomputers 17, 27 respectively.

In not shown memories mounted on the microcomputers 17, 27 are writtenprogrammed data of a distance detection method (distance detectionprogram), which will be described in the following. Incidentally, it ispreferable to use a magnetic recording medium such as a hard diskapparatus, a floppy disk, CD-ROM, CD-RW, and MO, an optical recordingmedium and an optical magnetic recording medium besides the aforesaidmemory as a recording medium for storing the distance detection program.

A signal line 18 (28) connecting between the antenna 16 (26) for both oftransmitting and receiving and the transmission system circuit 13 (25)or the reception system circuit 15 (22) corresponds to signal inputmeans. The reference numerals inserted in the parentheses indicate theconstituent elements on the communication station 20 side.

Incidentally, it is supposed that the period of the reference timer 11and the period of the other reference timer 21 are the same. It is alsosupposed that the time difference ΔT shown in FIG. 1 becomes >0(positive) when the time of the reference timer 21 of the othercommunication station 20 is earlier than the time of the reference timer11 of the one side communication station 10, and becomes <0 (negative)when the former is later than the latter. Moreover, the followingdescription will be given on the supposition that the timer of the otherside reference timer 21 is earlier than the time of the one sidereference timer 11.

Now, the one side communication station 10 transmits a signal having aperiod synchronized with the reference timing based on the referencetimer 11 (periodic signal) to the other side communication station 20.For simplifying the description, the transmission timing is supposed tobe the initial phase of the reference timer 11. When the other sidecommunication station 20 receives the periodic signal transmitted fromthe one side communication station 10, the other side communicationstation 20 transmits a periodic signal synchronized with the referencetiming based on the reference timer 21 in the communication station 20to the one side communication station 10. For simplifying thedescription, the transmission timing of the other side communicationstation 20 is supposed to be the initial phase of the reference timer21. Then, the one side communication station 10 receives the periodicsignal transmitted from the other side communication station 20 todetect the phase difference between the received periodic signal and thepreviously transmitted periodic signal, and then the communicationstation 10 corrects the signal delay time of the self station, whichwill be described later, on the basis of the detected phase difference.A distance is calculated by the use of the correction value.

The other side communication station 20 also detects, similarly, thephase difference on the basis of the transmission timing to the one sidecommunication station 10 and the reception timing, and further measuresthe signal delay time in the communication station 20. And then, thecommunication station 20 transmits the phase difference and the signaldelay time detected by the communication station 20 or the correctionvalue of the signal delay time corrected on the basis of the phasedifference to the one side communication station 10. As will bedescribed later, after the timer correction has been performed in acommunication station, the distance calculation becomes possible withoutreceiving the correction value of the opponent station.

Although the transmission timing of the transmission signals of thecommunication stations 10, 20 is supposed to be the initial phases ofrespective reference timers 11, 21 for the simplification of thedescription, the transmission timing is not necessarily the initialphase as long as the communication stations 10, 20 transmit thetransmission timing at the same phase.

The case described above is the case where the one side communicationstation 10 is a station that performs the distance measurement. In thecase where the other side communication station 20 is a station thatperforms the distance measurement, the transmission station and thereception station are exchanged.

Incidentally, although the description will hereinafter be given for thesimplification of the description to a case where the one sidecommunication station 10 transmits a transmission signal to the otherside communication station 20 for the measurement of a distance and theother side communication station 20 that received the transmissionsignal transmits the transmission signal for the measurement of thedistance back to the one side communication station 10 by the use of thetransmission signal as a trigger, the present invention is notrestricted to such a case. That is, when both of the communicationstations 10, 20 are communicating about a thing unrelated to themeasurement of distance, both the communication stations 10, 20 canseverally perform the measurement of distance by utilizing transmissionsignals and reception signals in the communication. When an opponentstation transmits a signal delay time in the transmission and receptioncircuit of the opponent station and correction information calculated byusing the signal delay time, it is considerable to use the informationby extracting from the reception signal.

Moreover, when the one side communication station 10 detects thedistance between the communication station 10 and the other sidecommunication station 20, the communication station 10 measures a signaldelay time of the transmission and reception circuit (the transmissionsystem circuit 13 and the reception system circuit 15), which causeserrors, in the one side communication station. That is, thecommunication station 10 measures the difference between thetransmission timing and the reception timing by turning back thetransmission signal at a signal line 18 to receive the tuned backtransmission signal. The communication station 10 corrects the distancemeasurement value with the measured value to cancel the signal delaytime at the transmission and reception circuit, and consequently highaccuracy distance detection become possible. Incidentally, in the casewhere the other side communication station 20 is a station that performsthe distance measurement, the other side communication station 20measures the signal delay time of the transmission and reception systemcircuit (the reception system circuit 22 and the transmission systemcircuit 25) in the communication station 20 to use the measured signaldelay time as a correction value.

Hereinafter, the distance detection method will be described.

Here, the signal delay time of the transmission system circuit 13 in thecommunication station 10 is supposed to be t1; the signal delay time ofthe reception system circuit 15 is supposed to be t4; the signal delaytime of the reception system circuit 22 in the communication station 20is supposed to be t2; and the signal delay time of the transmissionsystem circuit 25 is supposed to be t3.

The communication stations 10, 20 severally transmit a signal fordistance measurement to an opponent station on the basis of thereference timers 11, 21 of the self station, and receive a signal fordistance measurement from the opponent station to measure phasedifferences Ta, Tb between the signal transmitted from the self stationand the signal transmitted from the opponent station.

Moreover, respective communication stations 10, 20 turn backtransmission signals from the self stations at the signal lines 18, 28,and input the turned back transmission signals to the reception systemcircuits 15, 22 of the self stations to receive them. And then, thecommunication stations 10, 20 measure the differences between thetransmission timing and the reception timing at that time. The values oft1, t2, t3 and t4 cannot be measured separately in the measurements.However, the communication station 10 can measure the value of (t1+t4),and the communication station 20 can measure the value of (t2+t3). Inthis case, the value of (t1+t4) is a sum of respective signal delaytimes of the transmission system circuit 13 and the reception systemcircuit 15 in the communication station 10, and the value of (t2+t3) isa sum of respective signal delay times of the transmission systemcircuit 25 and the reception system circuit 22 in the communicationstation 20.

As apparent from FIG. 1, the relationships between the phase differencesTb, Ta, a signal propagation time T, the time differences ΔT, and thesignal delay times t1, t2, t3, t4 meet the following formulae (2), (3).

Ta=T+t 3+t 4−ΔT  (2)

Tb=T+t 1+t 2+ΔT  (3)

The communication stations 10, 20 perform the corrections of the phasedifferences Ta, Tb in conformity with the following formulae (4), (5) bythe use of signal delay times (t1+t4), (t2+t3), and transmit thecorrected phase differences Tah, Tbh to the opponent stations.

Tah=Ta−(t 1+t 4)  (4)

Tbh=Tb−(t 2+t 3)  (5)

When the signal delay times t1, t4, t2 and t3 are supposed to be zero,the relative distance R between the communication stations can bedetected by the following formula (6).

R=c×T=c×(Ta+Tb)/2  (6)

Where “c” indicates light velocity.

Because the signal delay times t1, t4, t2, and t3 are actually not zero,the Ta and Tb on the right side of the formula (6) are replaced by theTah, Tbh, and then the formulae (4), (5) are substituted to obtain thefollowing formula (7). Moreover, when the formulae (2), (3) aresubstituted, the following formula (8) is obtained.

c×(Tah+Tbh)/2=c×{Ta+Tb−(t 1+t 2+t 3+t 4)}/2  (7)

 c×(Tah+Tbh)/2=c×T  (8)

The formula (8) is nothing else but the following formula (9) that isthe formula (6) in which the Ta, Tb are substituted by the Tah, Tbh.Consequently, the relative distance R can be obtained in conformity withthe formula (9).

R=c×T=c×(Tah+Tbh)/2  (9)

On the other hand, the discrepancy quantity ΔTb (=−ΔT) of the referencetimer 21 in the other side communication station 20 from the referencetimer 11 in the one side communication station 10 when the referencetimer 11 in the communication station 10 is taken as a reference can beobtained in conformity with the following formula (10) in the case wherethe signal delay times t1, t4, t2 and t3 are supposed to be zero.

ΔTb=−ΔT=(Ta−Tb)/2  (10)

When the processing for the adjustment of the reference timer in thecommunication station 20 to the reference timer in the communicationstation 10 based on the timer discrepancy quantity ΔTb is performed andthe measurement phase differences are indicated by τa (communicationstation 10), τb (communication station 20), the measurement phasedifferences τa, τb are expressed by the following formulae (11)-(13).

τa=Ta+ΔTb=T  (11)

τb=Tb−ΔTb=T  (12)

R=c×T=c×τa=c×τb  (13)

Because the aforesaid processing is to turn back the other sidereference timer 21 by the time difference ΔT by the correction of thegains of the reference timer 21, the communication station 20 newlydetects a value obtained by the addition of the time difference ΔT tothe value Tb that has been detected as the reception timing until thattime. The value is the τb in the formula (12).

Until that time, the communication station 20 has transmitted signals atthe initial phase when the reference timer 11 in the communicationstation 10 is −ΔT. However, because the other side reference timer 21was corrected, the signals are transmitted with a retardation of thatperiod of time. Consequently, a value obtained by the subtraction of thetime difference ΔT from the value Ta that has been detected as thereception timing of the communication station 10 until that time isnewly detected. The newly detected value is the τa in the formula (11).

As it is known from the formulae (11)-(13), if the reference timers 11,21 are once set at the same time between the communication station 10and the communication station 20, the notification from awn opponentstation is hereafter unnecessary, and the relative distance R can bedetected only by the measurement of the reception timing of atransmission signal from the opponent station.

Because the signal delay times t1, t4, t2 and t3 are actually not zero,when the Ta, Tb on the right side of the formula (10) are replaced byTah, Tbh and formulae (4), (5) are substituted, the following formula(14) is obtained. Moreover, if the formulae (2), (3) are substituted,the following formula (15) can be obtained.

(Tbh−Tah)/2={Tb−Ta−(t 2+t 3−t 1−t 4)}/2  (14)

ΔTh=(Tbh−Tah)/2=ΔT+t 1−t 3  (15)

If the quantity ΔTbh of correction of the reference timer 21 in thecommunication station 20 is supposed to be −ΔTh in the case where thereference timer 21 in the communication station 20 is adjusted on thebasis of the reference timer 11 in the communication station 10, thedetection phase difference τa in the communication station 10 and thedetection phase difference τb in the communication station 20 after theadjustment of the reference timer 21 are expressed by the followingformulae (16), (17).

τa=Ta+ΔTbh  (16)

τb=Tb−ΔTbh  (17)

Because the gains of the reference timer 21 is corrected to turn backthe timer 21 by ΔTh similarly to the description about the formulae(11)-(13), the communication station 20 detects a new value obtained bythe addition of the ΔTh to the value Tb that has been detected as thereception timing until that time. The new value is the τb in the formula(17). Because the timer 21 was corrected although the communicationstation 20 transmitted a signal when the time of the communicationstation 10 was −ΔTh until that time, the signals is transmitted with theretardation of that period of time. Consequently, a value obtained bythe subtraction of the ΔTh from the value Ta that has been detected asthe reception timing of the communication station 10 until that time isnewly detected. The value is the τa in the formula (16).

When the formula (2) and (15) are substituted into the formula (16), thefollowing formula (18) is obtained. Moreover, when the formula (3) and(15) are substituted in to the formula (17), the following formula (19)is obtained.

τa=T+t 1+t 4  (18)

τb=T+t 2+t 3  (19)

If corrected phase differences obtained by the correction of the τa, τbin conformity with the aforesaid correction formulae (4), (5) aredesignated by τah, τbh, the phase differences τah, τbh is expressed bythe following formula (20) to be equal to the propagation time T of thepropagation signal.

T=τah=τbh  (20)

The following formula (21) obtained by the multiplication of the lightvelocity “c” to both the sides of the formula (20) is nothing else butthe formula (13) in which the τa, τb are replaced by the τah, τbh.

R=c×T=c×τah=c×τbh  (21)

As apparent from the aforesaid, when a sum value of the signal delaytimes t1, t4, t2 and t3 of the transmission system circuits 13, 25 andthe reception system circuits 15, 22 of the communication stations 10,20 is measured and a value obtained by the correction of the detectedphase differences Ta, Tb by the formulae (4), (5) is determined as thecorrection phase difference Tah+Tbh, then the relative distance Rbetween the communication station 10 and the communication station 20can be detected.

In particular, as described in the explanation concerning the formulae(14)-(21), although respective values of the time differences ΔT of thereference timers 11, 21, and the signal delay times t1, t2, t3 and t4 ofthe transmission and reception system circuits 13, 15, 22 and 25 cannotbe obtained, the relative distance R can be detected by the use of onlythe phase difference information measured in the self station after theadjustment of the reference timers 11, 21 of the communication station10 and the communication station 20.

Incidentally, in the case where the reference timer 11 of thecommunication station 10 is adjusted on the basis of the reference timer21 of the communication station 20, the adjustment may be performed bythe inversion of the sign of the correction quantity of the timer 21.

Moreover, after the determination of the correction quantity ΔTbh of thereference timer 21 in the communication station 20, the relativedistance R between the communication station 10 and the communicationstation 20 can be obtained in conformity with the formula (22).

 R=c×(Tah−ΔTbh)  (22)

As described above, in the distance detection apparatus according to theembodiment 1, the sum value of the delay times t1, t4 and the sum valueof the delay times t2, t3 of the transmission. system circuits 13, 25and the reception system circuits 15, 22 of the communication stations10, 20 are measured, and the sums of the signal delay times are used asthe correction values when the relative distance R is obtained.Consequently, the signal delay times of the signal transmission systemcircuits 13, 25 and the signal delay times of the reception systemcircuits 15, 22 are canceled, and thereby high accuracy distancedetection becomes possible.

(Embodiment 2)

The aforesaid distance detection apparatus according to the embodiment 1can be applied to an apparatus that needs distance information such as aposition cognition apparatus, a speed detection apparatus, an on-vehicleapparatus, a mobile, a fixed station and a traffic informationgeneration apparatus.

For example, a system in which a transmission signal transmitted by aradio apparatus of a car is reflected by the body of an opponent car andthe reflection wave is received will be considered. It is supposed thatthe communication station 10 in FIG. 1 is a radio apparatus of a selfcar and the communication station 20 is a radio apparatus of an opponentcar. Then, the signal delay times t2, t3 of the reception system circuit22 and the transmission system circuit 25 of the opponent car are zero,and the state is equivalent to the case where the time differences ΔT ofthe reference timers 11, 21 are zero. However, there is no informationof the correction phase difference Tbh from the radio apparatus of theopponent car. In this case, the distance R can be detected in conformitywith the formula (21).

R=c×{Ta−(t 1+t 4)}/2  (23)

where Ta designates a phase difference between the reception signal andthe transmission signal when the transmission signal from the radioapparatus of the self car is reflected on the body of the opponent carand the self car receives the reflection wave, i.e. the receptionsignal.

(Embodiment 3)

Another system in which a signal transmitted by the radio apparatus of aself car is received by the radio apparatus of an opponent car and theradio apparatus of the opponent car ideally transmits a response signalat a zero response time and further the self car receives the responsesignal will be considered. When the radio apparatus of the opponent carinforms the signal delay times t2+t3 of the reception system circuit 22and the transmission system circuit 25 to the radio apparatus of theself car, the distance R can be calculated in conformity with theformula (24). In this case also, there is no information of thecorrection phase difference Tbh from the radio apparatus of the opponentcar.

R=c×{Ta−(t 1+t 4)+(t 2+t 3)}/2  (24)

Because it is actually impossible to make the response time zero, thereis used as a measure against the problem a way in which the opponent carinforms the reception time T1 when the opponent car received thetransmission signal from the radio apparatus of the self car and thetransmission time T2 when the radio apparatus of the opponent cartransmitted a transmission signal to the radio apparatus of the selfcar. In this case also, because the radio apparatus of the opponent carinforms the signal delay time t2+t3 to the self car, the distance R canbe calculated.

(Embodiment 4)

Although the present invention can be applied to general radiocommunications systems, in the case where the invention is particularlyapplied to the spectrum spreading communication mode, an implementeddistance detection apparatus has excellent distance resolution, thesynchronization adjustment of the spreading code of a reception signalis equivalent to the measurement of the phase difference of the signalas it is. Consequently, it is easy to make the present inventionpracticable in conformity with the spectrum spreading communicationmethod.

Hereinafter, the accuracy of distance detection and the specificationsof radio communication will be described in the following including anembodiment.

The distance R can be measured by the measurement of the propagationtime T of an electromagnetic wave on one way by performing an exchangeof the electromagnetic wave between a measurement instrument and ameasurement object, and by the multiplication of the light velocity(c=3.0×10⁸ [m/s]) to the propagation time T. In this case, a distance dxcalculated by the multiplication of the light velocity “c” to the timeresolution dT of the propagation time T is the distance resolution. Onthe contrary, the dT calculated by the division of the allowable errorof distance dx by the light velocity is the allowable error of time.

When the application of the present invention to a car collisionprevention apparatus is considered, the communication stations 10, 20shown in FIG. 1 are radio communication stations for distance detectionto be mounted on cars.

Now, if it is supposed that the allowable distance error in themeasurement of the distance between a car and the one in front for theprevention of collision is the order of one meter, the allowable. errordT of measuring time is the order of about three nanoseconds. When aspectrum spreading signal is used as the distance measurement signal,the order of a chip rate for the obtainment of time resolutioncorresponding to the distance resolution of the order of one metering isabout 100 MHz. A spectrum spreading apparatus having a chip rate of theorder of 100 MHz can easily be realized. In this case, because the gatedelay time of the transmission and reception system circuits of acommunication apparatus is generally in an order of several tens orhundreds nanoseconds, gate delay errors cannot be neglected. Even if thegate delay time is corrected to be calculated as a designed value, thegate delay time scarcely accords with the designed value because thereis dispersion in the manufacture thereof.

Accordingly, if the distance detection method of the present inventionis applied, because the distance detection method of the invention turnsback transmission signals of self stations at signal lines 18, 28 toinput them into the reception system circuits 15, 22 and thereby phasedifferences between the transmission signals and the reception signals,which a:e received transmission signals, the gate delay errors includingthe dispersion in the manufacture can be measured in resolution of aboutthree nanoseconds.

Consequently, by the use of the distance detection method of the presentinvention, the measurement of the distance between a car and the one infront can be enabled in distance resolution of the order of one meter,and it becomes possible to realize a collision prevention apparatus at alevel of practical use.

(Embodiment 5)

As another embodiment, a position detection apparatus such as a locatorand a navigator in a cellular mobile telephone system can be realized.For example, the present invention can be applied to emergency servicesystems such as a police call system or a fire call system, or to aSearch for a stray child.

Incidentally, in the United States, an entrepreneur of a mobiletelephone business has an obligation of the detection of subscribers ata fixed accuracy and a fixed probability.

In the cellular mobile telephone system, one of the communicationstation 10 and the communication station 20 shown in FIG. 1 performs arole of a base station, and the other of the communication stations 10,20 performs a role of a mobile station.

If the accuracy of a cellular mobile telephone necessary for detecting aposition is about the order of 60 m, the distance resolution of 60 m isconverted into the time resolution of about 200 nanoseconds. It isconverted into the frequency resolution about 5 MHz. As a currentcellular CDMA system, IS 95 is made practicable, and the chip ratethereof is about 1.2 MHz. Accordingly, if over-sampling of about fourtimes is performed, the time resolution of the order of about 200nanoseconds can be realized. That is, telephone calls and distancedetection can simultaneously be realized in the radio specifications ofthe order in the same degree of the radio specifications of the spreadspectrum communication in conformity with IS 95.

(Embodiment 6)

Embodiment 6 of the present invention performs the distance detectionand the distance display service between mobile telephones.

In the embodiment 6, the communication stations 10, 20 shown in FIG. 1severally perform roles of mobile telephones, and telephone calls areexecuted between the two mobile telephones.

The order of the distance resolution thereof and the order of the chiprate of spectrum spreading thereof are almost the same as those of theposition detection apparatus such as the locator and the navigator ofthe cellular mobile telephone system of the aforesaid embodiment 5.

(Embodiment 7)

FIG. 2 is a block diagram showing the basic configuration of a generalcommunication apparatus in conformity with the spectrum spreadingcommunication mode according to embodiment 7 of the present invention.

As shown in the figure, the communication apparatus is configured so asto comprise a control section 120 including a CPU 121 for control and amemory 122, a transmission and reception section 130 including a radiocircuit 131, a spreading/despreading section 132 and an antenna 133 forboth of transmitting and receiving, a spreading code synchronizationacquisition/preservation section 140 including a digital signalprocessor (DSP) 141 and a memory 142, and a reference timer 150.

Because the antenna 133 for both of transmitting and receiving isconnected with both of a transmission system circuit and a receptionsystem circuit, a transmission, signal is turned back at the antennasection to be input to the reception system circuit as it is.

In the spectrum spreading communication, that a transmission signal ofself station is recognized as a reception signal from the opponentstation is prevented in conformity with the FDD system that utilizesdifferent carrier frequencies as the carrier frequency of a transmissionwave and the carrier frequency of a reception wave or the TDD systemthat separates the transmission timing and the reception timing andneglects reception signals during the transmission timing.

If a transmission signal of a self station is received by the selfstation, it can be realized by the TDD system unless the receptionsignal during the transmission timing is neglected. If the carrier ofthe transmission wave is supplied as a demodulation wave of thedemodulation circuit of signal reception, that can be realized in theFDD system.

Moreover, in the spectrum spreading communication, because thesynchronization acquisition and preservation by the spreading codesynchronization acquisition/preservation section 140 is the measurementof the reception timing as it is, it is not necessary to add newhardware for the measurement of the reception timing to the currenthardware configuration for performing the measurement of the receptiontiming of a turned back transmission signal from self station and asignal from an opponent station.

As an example of the spreading code synchronizationacquisition/preservation section 140, the illustration of a delayprofile is shown in FIG. 3. In the figure, correlation outputs aredetected in the whole phase scope, and a phase ψi at which thecorrelation output larger enough than noises is output is obtained, andthen the despreading is performed at the phase ψi in ordinarydemodulation.

In case of the detection of the distance between a car and the one infront, the time resolution when four times over-sampling at the chiprate of 100 MHz is performed is about 2.5 nanoseconds, and it isconverted to about 0.75 m of distance resolution.

Because the chip rate is 1.2 MHz in the CDMA system IS 95 that isactually applied as a cellular standard mobile telephone system, thetime resolution at the time of the four times over-sampling is about 200nanoseconds, and is converted to be about 60 m distance resolution.

As apparent from the aforesaid, the hardware configuration of a currentgeneral spectrum spreading communication apparatus meets the necessaryconditions of the hardware configuration of a distance measurementapparatus of the present invention. Accordingly the distance detectionapparatus of the present invention can easily be realized by storing aprogram realizing the method for detecting distance of the presentinvention into the memory 122 of the control means 120 in a currentgeneral spectrum spreading communication apparatus used as it is.

(Embodiment 8)

Although a spectrum spreading communication apparatus is described as anexample in the aforesaid embodiment 7, it is apparent that the presentinvention can be applied to the whole radio communication system. Thatis, it is realized only by the addition of reception timing measuringmeans capable of measuring at the time resolution converted from therequired distance resolution to the hardware configuration of acommunication apparatus.

This application is based on the Japanese Patent Application No. HEI11-210237 filed on Jul. 26, 1999, entire content of which is expresslyincorporated by reference herein.

Industrial Applicability

According to the present invention, in the distance measurement amongcommunication stations performing various communications, especially thecommunication in conformity with the spectrum spreading communicationmode, high accuracy distance detection can be performed.

What is claimed is:
 1. A distance detection apparatus, comprising: awireless transmission system circuit that transmits a transmissionsignal after performing signal processing of the transmission signal; awireless reception system circuit that performs signal processing of areception signal received from an object subjected to a distancemeasurement; a distance detection section that measures a signal delaytime in said wireless transmission system circuit and said wirelessreception system circuit, and corrects a distance measurement value,that is obtained by measuring a distance to the object, using a signaldelay time; a first reference timer that generates a first referencetiming; a signal generation section that generates a periodic signalsynchronized with the first reference timing to input the periodicsignal to said wireless transmission system circuit as the transmissionsignal, wherein said distance detection section detects a first phasedifference indicating a degree of a discrepancy of reception timing ofthe reception signal received from the object from the first referencetiming, and detects the distance to the object using the first phasedifference, the detected signal delay time, a second phase differenceand a signal delay time being detected at the object, said distancedetection section correcting the first phase difference using thedetected signal delay time to obtain a corrected phase difference, thedistance to the object being detected using the corrected phasedifference and an informed corrected phase difference informed by theobject, said distance detection section obtaining the corrected phasedifference in conformity with a formula: (corrected phasedifference)=(first phase difference)−(detected signal delay time). 2.The distance detection apparatus of claim 1, wherein said distancedetection section detects tire distance to the object in conformity witha following formula;  (distance)=K×((corrected phasedifference)+(informed corrected phase difference))/2  where K is aconstant corresponding to the velocity of light.
 3. A distance detectionapparatus, comprising: a wireless transmission system circuit thattransmits a transmission signal after performing signal processing ofthe transmission signal; a wireless reception system circuit thatperforms signal processing of a reception signal received from an objectsubjected to a distance measurement; a distance detection section thatmeasures a signal delay time in said wireless transmission systemcircuit and said wireless reception system circuit, and corrects adistance measurement value, that is obtained by measuring a distance tothe object, using a signal delay time; a first reference timer thatgenerates a first reference timing; a signal generation section thatgenerates a periodic signal synchronized with the first reference timingto input the periodic signal to said wireless transmission system as thetransmission signal, wherein said distance detection section detects afirst phase difference indicating a degree of a discrepancy of receptiontiming of the reception signal received from the object from the firstreference timing, and detects the distance to the object using the firstphase difference, the detected signal delay time, a second phasedifference and a signal delay time being detected at the object, saiddistance detection section correcting the first phase difference usingthe detected signal delay time to obtain a corrected phase difference,the distance to the object being detected using the corrected phasedifference and an informed corrected phase difference informed by theobject, a communication station having a second reference timer thatgenerates a second reference timing, the signal delay time beingmeasured at the object, a second phase difference indicating a degree ofa discrepancy of the reception timing of the reception signal from thesecond reference timing being detected, the second phase differencebeing corrected using the signal delay time at the object, the correctedphase difference being transmitted as the informed corrected phasedifference, said distance detection section determining a correctionquantity for an adjustment of the first reference timer and the secondreference timer using the corrected phase difference and the informedcorrected phase difference, said distance detection section determininga correction quantity of the second reference timer on a basis of thefirst reference timer in conformity with a formula; (correction quantityof second reference timer)=((corrected phase difference)−(informedcorrected phase difference))/2.
 4. A distance detection apparatus,comprising: a wireless transmission system circuit that transmits atransmission signal after performing signal processing of thetransmission signal; a wireless reception system circuit that performssignal processing of a reception signal received from an objectsubjected to a distance measurement; a distance detection section thatmeasures a signal delay time in said wireless transmission systemcircuit and said wireless reception system circuit, and correctsdistance measurement value, that is obtained by measuring a distance tothe object, using a signal delay time; a first reference timer thatgenerates a first reference timing; a signal generation section thatgenerates a periodic signal synchronized with the first reference timingto input the periodic signal to said wireless transmission systemcircuit as the transmission signal, wherein said distance detectionsection detects a first phase difference indicating a degree of adiscrepancy of reception timing of the reception signal received fromthe object from the first reference timing, and detects the distance tothe object using the first phase difference, the detected signal delaytime, a second phase difference and a signal delay time being detectedat the object, said distance detection section correcting the firstphase difference using the detected signal delay time to obtain acorrected phase difference, the distance to the object being detectedusing the corrected phase difference and an informed corrected phasedifference informed by the object, a communication station having asecond reference timer that generates a second reference timing, thesignal delay time being measured at the object, a second phasedifference indicating a degree of a discrepancy of the reception timingof the reception signal from the second reference timing being detected,the second phase difference being corrected using the signal delay timeat the object, the corrected phase difference being transmitted as theinformed corrected phase difference, said distance detection sectiondetermining a correction quantity for an adjustment of the firstreference timer and the second reference timer using the corrected phasedifference and the informed corrected phase difference, said distancedetection section determining a correction quantity of the firstreference timer on a basis of the second reference timer in conformitywith a formula; (correction quantity of first referencetimer)=((informed corrected phase difference)−(corrected phasedifference))/2.
 5. A distance detection apparatus, comprising: awireless transmission system circuit that transmits a transmissionsignal after performing signal processing of the transmission signal; awireless reception system circuit that performs signal processing of areception signal received from an object subjected to a distancemeasurement; a distance detection section that measures a signal delaytime in said wireless transmission system circuit and said wirelessreception system circuit, and corrects a distance measurement value,that is obtained by measuring a distance to the object, using a signaldelay time; a first reference timer that generates a first referencetiming; a signal generation section that generates a periodic signalsynchronized with the first reference timing to input the periodicsignal to said wireless transmission system circuit as the transmissionsignal, wherein said distance detection section detects a first phasedifference indicating a degree of a discrepancy of reception timing ofthe reception signal received from the object from the first referencetiming, and detects the distance to the object using the first phasedifference, the detected signal delay time, a second phase differenceand a signal delay time being detected at the object, said distancedetection section correcting the first phase difference using thedetected signal delay time to obtain a corrected phase difference, thedistance to the object being detected using the corrected phasedifference and an informed corrected phase difference informed by theobject, a communication station having a second reference timer thatgenerates a second reference timing, the signal delay time beingmeasured at the object, a second phase difference indicating a degree ofa discrepancy of the reception timing of the reception signal from thesecond reference timing being detected, the second phase differencebeing corrected using the signal delay time at the object, the correctedphase difference being transmitted as the informed corrected phasedifference, said distance detection section determining a correctionquantity for an adjustment of the first reference timer and the secondreference timer using the corrected phase difference and the informedcorrected phase difference, said distance detection section detectingthe distance to the object in conformity with a formula after saiddistance detection section performs the adjustment of the firstreference timer and the second reference timer; (distance)=K×(correctedphase difference), where K is a constant corresponding to the velocityof light.
 6. A distance detection apparatus, comprising: a wirelesstransmission system circuit that transmits a transmission signal afterperforming signal processing of the transmission signal; a wirelessreception system circuit that performs signal processing of a receptionsignal received from an object subjected to a distance measurement; adistance detection section that measures a signal delay time in saidwireless transmission system circuit and said wireless reception systemcircuit, and corrects a distance measurement value, that is obtained bymeasuring a distance to the object, using a signal delay time; a firstreference timer that generates a first reference timing; a signalgeneration section that generates a periodic signal synchronized withthe first reference timing to input the periodic signal to said wirelesstransmission system circuit as the transmission signal, wherein saiddistance detection section detects a first phase difference indicating adegree of a discrepancy of reception timing of the reception signalreceived from the object from the first reference timing and detects thedistance to the object using the first phase difference, the detectedsignal delay time, a second phase difference and a signal delay timebeing detected at the object, said distance detection section correctingthe first phase difference using the detected signal delay time toobtain a corrected phase difference, the distance to the object beingdetected using the corrected phase difference and an informed correctedphase difference informed by the object, a communication station havinga second reference timer that generates a second reference timing, thesignal delay time being measured at the object, a second phasedifference indicating a degree of a discrepancy of the reception timingof the reception signal from the second reference timing being detected,the second phase difference being corrected using the signal delay timeat the object, the corrected phase difference being transmitted as theinformed corrected phase difference, said distance detection sectiondetermining a correction quantity for an adjustment of the firstreference timer and the second reference timer using the corrected phasedifference and the informed corrected phase difference, said distancedetection section detecting the distance to the object in conformitywith a following formula after said distance detection sectiondetermines the correction quantity of the second reference timer;(distance)=K×((corrected phase difference)−(correction quantity ofsecond reference timer)), where K is a constant corresponding to thevelocity of light.
 7. A distance detection apparatus, comprising: awireless transmission system circuit that transmits a transmissionsignal after performing signal processing of the transmission signal; awireless reception system circuit that performs signal processing of areception signal received from an object subjected to a distancemeasurement; a distance detection section that measures a signal delaytime in said wireless transmission system circuit and said wirelessreception system circuit, and corrects a distance measurement value,that is obtained by measuring a distance to the object, using a signaldelay time; a first reference timer that generates a first referencetiming; and a signal generation section that generates a periodic signalsynchronized with the first reference timing to input the periodicsignal to said wireless transmission system circuit as the transmissionsignal, wherein said distance detection section detects a first phasedifference indicating a degree of a discrepancy of reception timing of areflection wave of the transmission signal reflected by the object fromthe first reference timing, and detects the distance to the object inconformity with a following formula; (distance)=K×((first phasedifference)−(detected signal delay time))/2,  where K is a constantcorresponding to the velocity of light.